Radiance

This project utilized the Radiance Lighting Simulation
and Rendering System (Radiance) to generate synthetic images. Radiance
is a suite of programs built around an advanced distributed raytracer
designed for realistic image synthesis. It was selected because it
is a physically-based rendering system designed to accurately model
the light behavior of a scene using physical units. Using such a system
reinforces the validity of the results obtained by the physics based
BRDFs within OBL and those generated from NEFDS.
Additionally, the source code to Radiance is publicly
available and the program is currently in wide use, aiding future
work.

Radiance is a distributed ray tracer which utilizes Monte Carlo importance
sampling to solve the rendering
equation. The rendering equation specifies the reflected radiance
in direction
from the values of the surface's BRDF and the incident irradiance,
integrated over all incident directions. As mentioned earlier the
solution of this integral often is the most computationally expensive
task of a rendering program. For this reason the solution to this
integral is often found through the use of Monte Carlo integration.

Radiance was designed with built-in support of arbitrary BRDFs, but
only for computing the direct contribution of the dominant light sources.
(In Radiance, the dominant light sources are handled separately to
reduce the variance introduced in the Monte Carlo evaluation of the
rendering equation.). In order to correctly handle the contribution
from the rest of the environment, a new shader, iBRDF,
was developed which uses Monte Carlo importance sampling.